A5025-A Phase II, Randomized Study of the Safety and Efficacy of Hydroxyurea in Patients on Potent Antiretroviral Therapy with less than 200 Copies/ml of HIV RNA in the Plasma. This study will explore whether hydroxyurea (HU) will enhance long-term suppression of HIV-1 replication in patients receiving triple therapy that includes two nucleoside analogs and a protease inhibitor. The primary endpoint of the study will be a combined endpoint, corresponding to the loss of viral suppression (HIV RNA > 200 copies/ml on 2 consecutive measures) or the occurrence of study drug toxicity. Three hundred ninety-nine (399) HIV positive subjects will be enrolled in the study and stratified based on participation versus non-participation in ACTG 343. Eligible subjects will have documented plasma HIV RNA < 200 copies/ml and must have received at least six (6) months on an antiretroviral regimen of IDV, ADV (or d4T) and 3TC. Subjects must have a current CD4 cell count > 200 cells/mm3 and must have had a CD4 cell count of > 100 cells/mm3 within the three (3) months prior to beginning the IDV/ADV (or d4T)/3TC regimen. Subjects cannot have any contraindication to d4T, ddl or HU. Subjects will be equally randomized to Step 1 treatment: Arm A: IDV 800mg Q8H +ddl 400mg QD+d4T 40mg BID+HU Placebo BID (N=133) Arm B: IDV 800mg Q8H+ddl 400mg QD+d4T 40mg BID+HU 600mg BID (N=133) Arm C: IDV 800mg Q8H+3TC 150mg/ZDV 300mg BID(or d4T 40mg BID+3TC 150mg BID)(N=133). For subjects <60kg in body weight, ddl will be administered at 250 mg QD and d4T will be administered at 30mg BID. Subjects will be treated for 24 months.